Sound only coming from one headphone

Hi guys, recording newbie here, would really appreciate it if you could help me out.

My problem is, when I select my interface (Edirol UA-4fx) as the option for playback, and i plug my headphones into it, sound only comes out of one side of the headphones when i play my recording. When I adjusted the panning 100% to the right, no sound comes out, when i have the panning in the middle, it only comes out of the left side and when i have the panning 100% to the left, its the exact same as when its in the middle, sound only from the left.

I’ve played the exact same recording through my speakers and sound comes from both of them. I’ve played music through my headphones and sound comes from both sides, so its not my headphones. I’ve tried setting the recording as ‘Mono’ and ‘Stereo’ and they’re both the same, sound only comes from the left.

Any ideas?
Thanks in advance.

What happens if you play from Windows Media Player through the UA-4fx?

Are you sure the headphone plug is all the way in? Left Only is one of the symptoms of a partially seated plug.

How new is the Edirol and has it ever worked?

There is one other thing you can try. Plug an RCA to RCA stereo cable into the Output L-R RCAs and play something. Jam your earbuds into first one side and then the other like this:

See if you get sound on one plug but not the other.